1. Field of the Invention
The present invention relates to a seat back of an automotive seat. In particular, the invention is directed to a combination of the seat back and a back board securely attached to that particular seat back.
2. Description of Prior Art
Generally stated in the filed of automotive seats, a back board for attachment to a rear side of a seat back is formed from a resin material, a hard board, a molded paper material, or the like. Normally, this sort of back board is formed to have an increased thickness by using one of those materials with a view to providing a structural rigidity and also the back board itself to be in a close contact with the contour of seat back. But, when it came to attaining a light weight of seat back for fuel economy purpose, it is required to reduce the thickness of the back board, in which case, the rigidity of the back board will become decreased, with the result that, when a backward load is applied to the seat back, a padding in the seat back is thereby pressed against the back board which is eventually deformed or damaged. Further, the reduced thickness of back board is insufficient to cause close contact of outer surfaces of the seat back with inward surfaces of the back board, so that some clearances are found between the back board and the areas of the seat back with which that particular back board is to be contacted, which results in impairing an outer aesthetic appearance of the seat back.
The Japanese Laid-Open Patent Publication No. 2003-189973 teaches a back board for seat back, wherein steel angle elements and the like are attached to and along inward corner portions of a relatively thin back board, thereby not only providing reinforcement to the back board sufficient to withstand a backward load applied thereto via a padding of the seat back, but also causing inner surfaces of the back board to be in close contact with the contour of rearward portions of the seat back.
However, at any rate, a heavy weight of the steel angle elements adversely increases a weight of the back board, resulting in an increased weight of seat back on the whole, and costs involved in forming and securing such steel angle elements to the back board are rather expensive.